Middle Atmosphere Research Articles

A new perspective on Saturn’s polar vortices: Coupling the thermosphere and stratosphere

We argue that the observed temperature and altitude structure at the base of Saturn’s polar thermosphere implies the presence of a deep, warm-cored, anticyclonic vortex that extends deep into the mesosphere, and possibly into the stratosphere. This would be a unique structure in the solar system: a permanent, large-scale middle atmospheric feature that is a direct consequence of magnetosphere-atmosphere coupling. We investigate the plausibility of the suggestion that this deep vortex is linked to the observed non-seasonal polar hotspots in Saturn’s stratosphere. We develop a simple model of the dynamics and thermal structure of the middle atmosphere polar vortex, assuming vertical viscous transport is dominant and that the zonal winds are close to geostrophic balance. The model requires the existence of a small poleward ageostrophic wind which causes compressional heating, producing the required pressure gradients. This scenario is supported by a re-analysis of previously published thermospheric modelling results. Using this model we estimate the extent to which the thermospheric vortex penetrates into the deeper atmosphere. The results are very sensitive to the distribution of eddy viscosity. The models which best match the thermospheric temperatures produce a polar hotspot in the stratosphere that is hotter and broader than observed, indicating that our model, while a useful starting point, is incomplete. We also point out a puzzle concerning the half-widths of the polar hotspot and the polar altitude bulge at the base of the thermosphere. We are able to explain the greater width of the hotspot provided that there is enhanced downwards vertical transport of angular momentum closer to the pole, a situation that is expected given the strong convergence and downwelling predicted in this region. Finally, we speculate that the tropospheric polar cyclone could be connected to the anticyclonic vortex in the thermosphere.

Estimates of Southern Hemispheric Gravity Wave Momentum Fluxes across Observations, Reanalyses, and Kilometer-Scale Numerical Weather Prediction Model

Abstract Gravity waves (GWs) are among the key drivers of the meridional overturning circulation in the mesosphere and upper stratosphere. Their representation in climate models suffers from insufficient resolution and limited observational constraints on their parameterizations. This obscures assessments of middle atmospheric circulation changes in a changing climate. This study presents a comprehensive analysis of stratospheric GW activity above and downstream of the Andes from 1 to 15 August 2019, with special focus on GW representation ranging from an unprecedented kilometer-scale global forecast model (1.4 km ECMWF IFS), ground-based Rayleigh lidar (CORAL) observations, modern reanalysis (ERA5), to a coarse-resolution climate model (EMAC). Resolved vertical flux of zonal GW momentum (GWMF) is found to be stronger by a factor of at least 2–2.5 in IFS compared to ERA5. Compared to resolved GWMF in IFS, parameterizations in ERA5 and EMAC continue to inaccurately generate excessive GWMF poleward of 60°S, yielding prominent differences between resolved and parameterized GWMFs. A like-to-like validation of GW profiles in IFS and ERA5 reveals similar wave structures. Still, even at ∼1 km resolution, the resolved waves in IFS are weaker than those observed by lidar. Further, GWMF estimates across datasets reveal that temperature-based proxies, based on midfrequency approximations for linear GWs, overestimate GWMF due to simplifications and uncertainties in GW wavelength estimation from data. Overall, the analysis provides GWMF benchmarks for parameterization validation and calls for three-dimensional GW parameterizations, better upper-boundary treatment, and vertical resolution increases commensurate with increases in horizontal resolution in models, for a more realistic GW analysis. Significance Statement Gravity wave–induced momentum forcing forms a key component of the middle atmospheric circulation. However, complete knowledge of gravity waves, their atmospheric effects, and their long-term trends are obscured due to limited global observations, and the inability of current climate models to fully resolve them. This study combines a kilometer-scale forecast model, modern reanalysis, and a coarse-resolution climate model to first compare the resolved and parameterized momentum fluxes by gravity waves generated over the Andes, and then evaluate the fluxes using a state-of-the-art ground-based Rayleigh lidar. Our analysis reveals shortcomings in current model parameterizations of gravity waves in the middle atmosphere and highlights the sensitivity of the estimated flux to the formulation used.

Disturbances in the Circulation of the Lower and Middle Atmosphere That Can be Caused by an Isolated Mountain Range

Disturbances in the Circulation of the Lower and Middle Atmosphere That Can be Caused by an Isolated Mountain Range

Probing atmospheric waves and the middle atmosphere dynamics using infrasound

Infrasound is defined as pressure fluctuations with frequencies between acoustic cut-off (5 min) and human-hearing frequency threshold of sound (16 Hz). Low-frequent infrasonic waves can travel long distances, ranging from hundreds to thousands of kilometres. The middle atmosphere dynamics mainly control the presence of atmospheric waveguides where energy transmission loss is low. These properties are utilized to record atmospheric explosions at highly sensitive pressure sensors (micro-barometers). A global network of 60 infrasound stations was designed as part of the International Monitoring System (IMS) for the Comprehensive Nuclear-Test-Ban Treaty. IMS infrasound stations can record small pressure fluctuations of a few millipascals, which can originate from numerous atmospheric infrasound sources, including meteorological phenomena. In this study, the capability of IMS infrasound arrays for capturing a broad spectrum of atmospheric wave phenomena is highlighted; for instance, mountain-associated infrasonic waves show features that seem to be correlated with orographic gravity waves. Moreover, the interaction of ocean waves produces quasi-continuous infrasound, so-called microbaroms. Infrasonic signatures from microbaroms can be used for probing the middle atmosphere dynamics and assessing atmospheric circulation models. For opening the unique global infrasound network of the IMS for meteorological applications, we also present open-access BGR infrasound data products of two decades and highlight selected case studies.

Passive Optical Observation of Mesosphere and Thermosphere Wind Over Three Stations in China

AbstractFabry Perot interferometer (FPI) is an essential ground‐based passive optical observation device to detect middle and upper atmospheric information. Three FPIs are located at Kunming (103.8°E, 25.6°N), Xinglong (117.4°E, 40.2°N), and Mohe (122.3°E, 53.5°N), China. The diurnal and annual variation of night wind at 87, 97, and 250 km are investigated from 2019 to 2021, compared to Horizontal Wind Model 14 (HWM14) to check the prediction accuracy for the local wind field. Our results are as follows: (a) At 87 km, the zonal winds are similar in Kunming and Xinglong, but the meridional winds are generally stronger in Kunming. The zonal and meridional winds in both locations are dominated by semidiurnal variations. (b) At 97 km, the duration of semidiurnal variation of zonal winds and diurnal variation of meridional winds in Kunming is long, which is opposite to that of Xinglong. (c) At 250 km, the wind speed increases with latitude for both zonal and meridional winds, which are both dominated by diurnal variations for all the three sites. Unlike 87 and 97 km, the entire wind field at 250 km is dominated by annual variation, except for a significant semiannual variation at midnight in Mohe. (d) Overall, the HWM14 predictions are stronger than the FPI measurements at peak wind speeds and similar at 87 and 97 km, which surpasses the performance at 250 km. Especially at 250 km, the model results are worse for the zonal winds of Kunming and the meridional winds of Mohe. These results will help to understand the wind field in the middle and upper atmosphere and improve the accuracy of the model.

Machine Learning Emulation of Subgrid‐Scale Orographic Gravity Wave Drag in a General Circulation Model With Middle Atmosphere Extension

AbstractGravity wave parameterizations contribute to uncertainties in middle atmosphere modeling. To investigate the potential for using machine learning to represent atmospheric gravity waves and the impact of implementing such schemes in a general circulation model (GCM), we train a random forest (RF) emulator on outputs from an existing complex parameterization scheme for orographic gravity wave drag (GWD). The performance of the RF emulator is then evaluated with a focus on stratospheric climatology and variability in climate simulations from the middle atmosphere resolving Beijing Climate Center Atmospheric Circulation Model. In offline tests, the predicted orographic GWD by the RF agrees remarkably well with the target GWD throughout the troposphere and the middle atmosphere. The RF emulator can reproduce the observed climatology of zonal‐mean wind and air temperature in the GCM simulation, as well as its target scheme. Compared to the target orographic GWD parameterization scheme, the RF emulator can reproduce the breakdown of the polar vortex in the Southern Hemisphere stratosphere. This study demonstrates the feasibility of using machine learning to emulate parameterized orographic GWD for modeling the stratosphere with a GCM.

Interannual Variability of Winds in the Antarctic Mesosphere and Lower Thermosphere Over Rothera (67°S, 68°W) During 2005–2021 in Meteor Radar Observations and WACCM‐X

AbstractThe mesosphere and lower thermosphere (MLT) plays a critical role in linking the middle and upper atmosphere. However, many General Circulation Models do not model the MLT and those that do remain poorly constrained. We use long‐term meteor radar observations (2005–2021) from Rothera (67°S, 68°W) on the Antarctic Peninsula to evaluate the Whole Atmosphere Community Climate Model with thermosphere‐ionosphere eXtension (WACCM‐X) and investigate interannual variability. We find some significant differences between WACCM‐X and observations. In particular, at upper heights, observations reveal eastwards wintertime (April–September) winds, whereas the model predicts westwards winds. In summer (October–March), the observed winds are northwards but predictions are southwards. Both the model and observations reveal significant interannual variability. We characterize the trend and the correlation between the winds and key phenomena: (a) the 11‐year solar cycle, (b) El Niño Southern Oscillation, (c) Quasi‐Biennial Oscillation and (d) Southern Annular Mode using a linear regression method. Observations of the zonal wind show significant changes with time. The summertime westwards wind near 80 km is weakening by up to 4–5 ms−1 per decade, whilst the eastward wintertime winds around 85–95 km are strengthening at by around 7 ms−1 per decade. We find that at some times of year there are significant correlations between the phenomena and the observed/modeled winds. The significance of this work lies in quantifying the biases in a leading General Circulation Model and demonstrating notable interannual variability in both modeled and observed winds.

Coupling of Long‐Term Trends of Zonal Winds Between the Mesopause and Stratosphere in Southern Winter

AbstractWe examine the relationships between the observed long‐term trends of the zonal wind in the mesopause regions at King Sejong Station (KSS), Antarctica, and wind trends in the Southern Hemisphere (SH) middle atmosphere using the 15‐year data set from KSS meteor radar, Aura MLS and MERRA‐2. During July, significant positive trends of zonal winds appear above z = 90 km and near the stratopause over the KSS, while negative trends exist between the two layers. In the SH winter, the observed mesopause winds correlate positively (negatively) with stratospheric (mesospheric) winds in the polar region, while they exhibit opposite correlations with the low‐latitude winds. The positive mesopause trends of zonal winds near KSS are connected, through the thermal wind relationship, to cooling (warming) trends induced by the upward (downward) trends of residual circulation over the high‐latitude mesosphere and low‐latitude stratosphere (high‐latitude stratosphere), which shows vertical coupling throughout the SH winter middle atmosphere.

Observations of polar mesospheric summer echoes resembling kilometer-scale varicose-mode flows

Abstract. The mesosphere and lower thermosphere (MLT) region represents a captivating yet challenging field of research. Remote sensing techniques, such as radar, have proven invaluable for investigating this domain. The Middle Atmosphere Alomar Radar System (MAARSY), located in northern Norway (69∘ N, 16∘ E), uses polar mesospheric summer echoes (PMSEs) as tracers to study MLT dynamics across multiple scales. Chau et al. (2021) recently discovered a spatiotemporally highly localized event showing a varicose mode (simultaneous upward and downward movements), which is characterized by extreme vertical velocities (|w|≥3σ) of up to 60 m s−1 in the vertical drafts. Motivated by this finding, our objective is to identify and quantify similar extreme events or comparable varicose structures, i.e., defined by quasi-simultaneous updrafts and downdrafts, that may have been previously overlooked or filtered out. To achieve this, we conducted a thorough manual search through a MAARSY dataset, considering the PMSE months (i.e., May, June, July, August) spanning from 2015 to 2021. This search has revealed that these structures do indeed occur relatively frequently with an occurrence rate of up to 2.5 % per month. Over the 7-year period, we observed and recorded more than 700 varicose-mode events with a total duration of about 265 h and documented their vertical extent, vertical velocity characteristics, duration, and their occurrence behavior. Remarkably, these events manifest throughout the entire PMSE season with pronounced occurrence rates in June and July, while the probability of their occurrence decreases towards the beginning and end of the PMSE seasons. Furthermore, their diurnal variability aligns with that of PMSEs. On average, the observed events persisted for 20 min, while the varicose mode caused an average expansion of the PMSE layer by a factor of 1.5, with a maximum vertical expansion averaging around 8 km. Notably, a careful examination of the vertical velocities associated with these events confirmed that approximately 17 % surpassed the 3σ threshold, highlighting their non-Gaussian velocity distribution and extreme nature.

Enhanced prediction of premonsoon thunderstorms over eastern India through assimilation of INSAT‐3D sounding data

AbstractThe present study assesses the impact of Indian National Satellite 3D (INSAT‐3D)‐derived atmospheric (temperature and relative humidity) profiles on the simulation of severe thunderstorms over eastern India during the premonsoon season. Two sets of numerical experiments, without assimilation (CNTL) and with assimilation of INSAT‐3D profiles (INSAT) have been conducted using the three‐dimensional variational data assimilation system of the Weather Research and Forecasting model for 11 thunderstorm events. Analysis increments are positive with INSAT profile assimilation in the lower to middle atmosphere in the thunderstorm region. The errors in the initial fields have been reduced by approx. 50% after the assimilation. After assimilation, the predictions of the surface fields (2‐m temperature, 2‐m relative humidity, and 10‐m wind speed) have been improved at the mature stage (by 37%, 26%, and 15%) compared to the CNTL. Similar improvements are noticed in the vertical profiles of relative humidity and wind speed in the INSAT experiment. The time and magnitude of updrafts and downdrafts improved in INSAT. After assimilation, rainfall intensity improved in nine cases, and time improved in four cases out of 11. The Critical Success Index (False Alarm Rate) of the INSAT ranges from approx. 0.6–0.15 (∼0.37–0.48) for all thresholds, and are higher (lower) than the CNTL. The rainfall area is improved by 25% for light rainfall, 11% for moderate rainfall, and 2% for heavy rainfall in the INSAT over the CNTL experiment. Overall thunderstorm prediction has been improved with the assimilation of INSAT‐3D data. Thus, the study highlights the viability of INSAT‐3D profiles in improving thunderstorm predictions over eastern India.

Ultra‐Fast Kelvin Wave Packets in Mars' Atmosphere and Their Interactions With Tides as Viewed by MAVEN/NGIMS and MRO/MCS

AbstractA key element of successful aerobraking operations at Mars is accurate thermospheric density predictions. Evidence suggests that much of the longitude variability in Mars' aerobraking region is associated with atmospheric tides, and the day‐to‐day variability is connected with tidal modulation by longer‐period global‐scale waves. Specifically, ultra‐fast Kelvin waves (UFKWs) and their modulation of the tidal spectrum play a key role in coupling Mars' lower (<∼80 km) and middle (∼80–100 km) atmosphere with the aerobraking region above. In this study, over 5 years of Mars Atmosphere and Volatile Evolution Neutral Gas and Ion Mass Spectrometer CO2 density observations are employed to reveal prominent, frequent, and persistent 2.5‐ to 4.5‐day UFKW packets in the whole Martian middle and upper thermosphere (ca. 150–200 km), and large secondary waves arising from their nonlinear interactions with the tidal spectrum. Detailed analyses focusing on a prominent ∼2.5‐day UFKW event in late 2015 demonstrate primary and secondary wave amplitudes growing twofold with altitude from ∼7%–14% near 150 km to ∼12%–25% near 200 km and their combined effects to account for ∼60%–80% of the altitude‐longitudinal variability of Mars' thermospheric density. Concurrent temperature measurements from Mars Reconnaissance Orbiter Mars Climate Sounder reveal consistent wave signatures near 80 km altitude suggesting propagation of both primary and secondary waves from the lower atmosphere. This study demonstrates that UFKWs and secondary waves from UFKW‐tide interactions are sources of significant altitude‐longitude variability in the Mars' aerobraking region that should be accounted for when analyzing satellite observations and nonlinear models.

Analysis of Atmospheric Elements in Near Space Based on Meteorological-Rocket Soundings over the East China Sea

As an important means of in situ detection in near space, meteorological rockets can provide a high-precision distribution analysis of atmospheric elements. However, there are currently few studies on the principles of meteorological-rocket detection and the application of rocket-sounding data. The purpose of this paper is to fill this gap by providing a detailed introduction to the detection principle of a meteorological rocket launched in the East China Sea in November 2022. Moreover, empirical models, satellite data, and reanalysis data were selected for comparison and verification with the rocket-sounding data. Furthermore, the accuracy of these widely used datasets was studied based on the rocket-sounding data in the near space over the East China Sea. Additionally, gravity-wave power–frequency spectra were extracted using the maximum entropy method from both the rocket-sounding data and the remote-sensing data. Furthermore, the relationship between gravity waves and Kelvin–Helmholtz instability (KHI) was investigated by analyzing the gravity-wave energy and the Richardson number. The research findings indicate that among the remote-sensing data describing the atmospheric environment over the launch site, the COSMIC occultation data is more accurate compared with the SABER data. The wind-field distribution derived from rocket detection is consistent with the Modern-Era Retrospective analysis for Research and Applications (MERRA) reanalysis data, while also providing a more detailed description of the wind field. The main wavelengths of gravity waves extracted from rocket-sounding data are consistently smaller than those obtained from satellite remote-sensing data, indicating that rocket sounding is capable of capturing more intricate structures of gravity waves. The good correspondence between the peaks of gravity-wave energy and the regions where KHI occurs indicates that there is a strong interaction between gravity waves and KHI in the middle atmosphere.

Low latitude mesospheric clouds in a warmer climate

AbstractObservations show that mesospheric clouds (MCs) have been increasing in recent decades, presumably due to increased mesospheric water vapor which is mainly caused by greater methane (CH4) oxidation in the middle atmosphere. Past warm climates such as those of the early Cretaceous and Paleogene periods are thought to have had higher CH4 concentrations than present day, and future CH4 concentrations will also likely continue to rise. Here, idealized atmosphere chemistry‐climate model experiments forced with strong polar‐amplified sea‐surface temperatures and elevated carbon dioxide (CO2) and CH4 concentrations predict a substantial spreading of MCs to middle and low latitudes, well beyond regions where they are currently found. Sensitivity tests show that increased water vapor from CH4 oxidation and cooling from increased CO2 and CH4 concentrations create favorable conditions for cloud formation, producing MC fractions of 0.02 in the low latitudes and 0.1 in the mid‐latitudes in the Northern Hemisphere when CH4 concentration is 16× higher than pre‐industrial. Further increases in CH4 result in a monotonic increase in low‐ and mid‐latitude MCs. A uniform surface ocean warming, changes in polar amplification, or the solar constant do not significantly affect our results. While the appearance of these clouds is interesting, their ice and liquid water content is not sufficient to cause a significant radiative effect. On the other hand, dehydration of the mesosphere due to these low‐ and mid‐latitude MCs could potentially lead to a reduction in atomic hydrogen, thereby affecting mesospheric ozone concentration, although further study is required to confirm this.

Characteristics and Mechanism of Interhemispheric Coupling in Austral Winter Revealed by Long‐Term Reanalysis Data for the Whole Middle Atmosphere

AbstractGlobal characteristics of dynamical fields for the interhemispheric coupling (IHC) initiated with a sudden stratospheric warming (SSW) in the southern hemisphere in the austral winter were examined using the global reanalysis for the whole neutral atmosphere from a data assimilation with satellite observations over 15 years of 2005–2019. Even in the austral winter, a strong cold equatorial stratosphere associated with the SSW, which is essential for the IHC, occurs about once every two years. The mechanism of the IHC in the austral winter is basically similar to that in the boreal winter. However, there are two significant differences in the IHC characteristics between the austral and boreal winters. One is that the SSW in the austral winter occurs mainly at midlatitudes, whereas the SSW in the boreal winter occurs mainly at high latitudes. As a result, a warm temperature anomaly simultaneously appears in the southern polar mesosphere in the austral winter, which is not observed for the boreal winter. The other is related to the seasonal variation of the quasi‐two‐day wave activity and induced forcing and gravity wave forcing in the summer mesosphere. For the IHC events occurring in July, when these wave activities and forcings are high, the response in the summer mesosphere is similar to that of the boreal winter. In contrast, for late August and September, when these wave forcings are weak, the response in the summer mesosphere is small. This result indicates that the IHC characteristics are largely influenced by the seasonal variation of these waves.

The Study of Internal Gravity Waves in the Earth’s Atmosphere by Radio Occultations: A Review

Internal gravity waves (IGWs) in the middle atmosphere are the main source of mesoscale fluctuations of wind and temperature. The parameterization of IGWs and study of their climatology is necessary for the development of global atmospheric circulation models. In this review, we focus on the application of Radio Occultation (RO) observations for the retrieval of IGW parameters. (1) The simplest approach employs the retrieved temperature profiles. It is based on the fact that IGWs are highly anisotropic structures and can be accurately retrieved by RO. The basic assumption is that all the temperature fluctuations are caused by IGWs. The smoothed background temperature profile defines the the Brunt–Väisälä frequency, which, together with the temperature fluctuations, defines the IGW specific potential energy. Many studies have derived the distribution and climatology of potential energy, which is one of the most important characteristics of IGWs. (2) More detailed analysis of the temperature profiles is based on the derivation of the temperature fluctuation spectra. For saturated IGWs, the spectra must obey the power law with an exponent of −3. Such spectra are obtained by using Wave Optical (WO) processing. (3) More advanced analysis employs space–frequency analysis. It is based on phase-sensitive techniques like cross S- or wavelet transforms in order to identify propagating IGWs. (4) Another direction is the IGW parameter estimate from separate temperature profiles applying the stability condition in terms of the Richardson number. In this framework, a necessary condition is formulated that defines whether or not the temperature fluctuations can be related to IGW events. The temperature profile retrieval involves integral transforms and filtering that constitute the observation filter. (5) A simpler filter is implemented by the analysis of the RO amplitude fluctuation spectra, based on the diffraction theory in the framework of the phase screen and weak fluctuation approximations. The two spectral parameters, the external scale and the structural characteristic, define the specific potential energy. This approach allows the derivation of the spacial and seasonal distributions of IGW activity. We conclude that the success of IGW study by RO is stimulated by a large number of RO observations and advanced techniques based on Fourier and space–time analysis, physical equations describing IGWs, and diffraction theory.

SPECTRA OF ANOMALOUS COSMIC RAYS IN ATMOSPHERE. SINGLY IONIZED AND MULTIPLY CHARGED ACR COMPONENTS

The Anomalous Cosmic Ray (ACR) spectra and intensity in the middle atmosphere are determined using the CORSIMA (COsmic Ray Spectra and Intensity in Middle Atmosphere) model. ACR spectra are presented for various atmospheric altitudes within the range of 40–50 km, with the lower boundary of the ionosphere at approximately 50 km. Experimental satellite measurements are utilized for the main ACR constituents Helium and Oxygen nuclei. It is found that the influence of ACRs extends to the polar cap regions above 65°–70° geomagnetic latitude, and certain ACR ionization rate values in these regions are comparable to Galactic Cosmic Ray (GCR) ionization rates. Our studies also consider Multiply Charged Anomalous Cosmic Rays (MCACRs), which exhibit similar differential spectra to the singly ionized ACR component4.

Tropical cyclone FANTALA's three turnbacks in the northeast of Madagascar Island.

The unique Tropical cyclone (TC) Fantala appeared in the central Indian Ocean (12.4°S, 73.5°E) at 00Z on April 11 in 2016 and moved northwestward along the northeast of Madagascar at 18 Z on April 15. Then, two incomprehensible turnbacks formed a unique TC track. The dynamic mechanisms of the three turnbacks were first studied based on remote sensing and multisource reanalysis data. The results reveal that the wind field with upper divergence and lower convergence promotes the development of Fantala. The anticyclone high pressure on the middle level atmosphere is an important factor for TC turnbacks. On 15 April, the TC made the first turnback to turn northwest due to the southward anticyclone weakened to moving northwest. On 18 April, the TC made the second turnback along the anticyclone edge due to the northern high-pressure and southern low-pressure trough. On 22 April, the TC made the third turnback because the anticyclonic high press center broke into two small independent anticyclonic centers in the southwest and northeast, which created a barrier band and pushed the northern TC to move to the northwest. Meanwhile, the vertical wind shear (VWS) also provides favorable conditions for TC turnbacks. On April 18, the middle atmosphere of the TC was affected by strong easterly shear and weak southerly shear, and the second turnback was completed. On April 22, the middle level environment was affected by strong westerly shear and weak north shear, and the third turnback was completed. Additionally, heat transport from the ocean to the atmosphere provides favorable conditions for TC development. On April 18, The maximum mean latent heat flux over northeastern Madagascar was 112.94 W/m2, Tropical Cyclone Heat Potential was 39.05 kJ/cm2, and the maximum wind speed at the center of the TC was 155 kts. On April 22, The heat transfer from the equator increased by 18.08 W/m2 compared with the latent heat on 21 April, the Tropical Cyclone Heat Potential was 33.30 kJ/cm2, the maximum wind speed in the TC center was 90 kts, the high PV centerspread down from 850 mb to 900 mb. This study deepens the understanding of track forecasting during the development of a TC.

The Study of Characteristics and Imaging of Infrared Radiation of Middle and Upper Atmosphere Background

The Study of Characteristics and Imaging of Infrared Radiation of Middle and Upper Atmosphere Background

Overview of Optical Interferometer Payloads for Detecting Wind Fields in Middle and Upper Atmosphere (Invited)

Overview of Optical Interferometer Payloads for Detecting Wind Fields in Middle and Upper Atmosphere (Invited)

Photodetachment rates for O⁻ and O₂⁻ in the D layer of the ionosphere as function of solar zenith angle and solar activity

We present the results of calculation of photodetachment rates for negative ions in the D layer of the ionosphere, using recent photodetachment cross-section measurements. The calculations have been made for the standard atmosphere by means of the TUV (Terrestrial UltraViolet) code. We have obtained dependences of the photodetachment rates on altitude and solar zenith angle. The nonlinear nature of these dependences causes similar variations in the role of the photodetachement processes with altitude and solar zenith angle as compared to other processes in the middle atmosphere and the lower ionosphere, especially under terminator conditions. Calculations with solar spectrum for 2011–2020 for the summer/winter solstice and the spring/autumn equinox have shown no quantitative difference between the photodetachement rates for ions in the D layer of the ionosphere.